Transcript Percent Increase/Decrease

Percent Increase/Decrease and
Percent Error
• Cassandra likes rings. She currently has 5 rings in her
collection.
– Draw a double number line diagram relating the number
of rings as a percent of the whole set of rings.
– What percent is represented by the whole collection of
rings?
– What percent of the collection does each ring represent?
• Cassandra’s aunt said she will buy Cassandra
another ring for her birthday. If Cassandra gets
the ring for her birthday, what will be the
percent increase in her ring collection?
increase
0%
100%
120%
• Jon increased his trading card collection by 5
cards. He originally had 15 cards. What is the
percent increase?
• Suppose instead of increasing the collection by 5
cards, John increased his 15-card collection by
just 1 card. Will the percent increase be the same
as when Cassandra’s ring collection increased by
1 ring (in Example 1)? Why or why not? Explain.
Formula For Percent
Increase/Decrease and Percent Error
𝑪𝒉𝒂𝒏𝒈𝒆
𝑶𝒓𝒊𝒈𝒊𝒏𝒂𝒍
x 100 = percent change or percent error
• Ken said that he is going to reduce the
number of calories that he eats during the
day. Ken’s trainer asked him to start off small
and reduce the number of calories by no more
than 7%. Ken estimated and consumed 2,200
calories per day instead of his normal 2,500
calories per day until his next visit with the
trainer. Did Ken reduce his calorie intake by
7%? Justify your answer.
𝟑𝟎𝟎
𝟐𝟓𝟎𝟎
= .12 or 12% change
• How many calories would Ken need to
consume for an exact change in calories of
7%? (he normally eats 2,500)
• “The value of an investment decreased by
10%. The original amount of the investment
was $75. What is the current value of the
investment?”
• Justin earned 8 badges in Scouts as of the Scout
Master’s last report. Justin wants to complete 2 more
badges so that he will have a total of 10 badges earned
before the Scout Master’s next report.
– a. If Justin completes the additional 2 badges, what will be
the percent increase in badges?
– b. Express the 10 badges as a percent of the 8 badges.
– c. Does 100% plus your answer in part (a) equal your
answer in part (b)? Why or why not?
• A realtor expected 18 people to show up for
an open house, but 25 attended. What is the
percent error of the realtor’s prediction?
• In science class, Mrs. Moore’s students were
directed to weigh a 300 gram mass on the
balance scale. Tina weighed the object and
reported 328 grams. What was the percent
error of Tina’s measurement?
• Darwin’s coach recorded that he had bowled
250 points out of 300 in a bowling
tournament. However, the official scoreboard
showed that Darwin actually bowled 225
points out of 300. What was the percent error
the coach made?
• The veterinarian weighed Oliver’s new puppy,
Boaz, on a defective scale. He weighed 36
pounds. However, Boaz weighs exactly 34.5
pounds. What is the percent of error in
measurement of the defective scale to the
nearest tenth?
• Erin wants to raise her math grade to a 95 to
improve her chances of winning a math
scholarship. Her math average for the last
marking period was an 81. Erin decides she
must raise her math average by 15% to meet
her goal. Do you agree? Why or why not?
Support your written answer by showing your
math work.
– (hint: not 15 points, 15% of her current math
average)